Burner unit

ABSTRACT

A burner unit for fluid fuels and also for pulverized coal comprising combustion chamber means, prechamber means, means to enable combustion gases to pass from said combustion chamber means into said prechamber means, mixing pipe means in communication with said prechamber means and said combustion chambers means, a fuel supply nozzle for distributing finely divided fuel towards said mixing pipe means into the drawn-in combustion gases, and means for supplying oxygen-containing gas, f.i. air, to the mixture of fuel and combustion gases, wherein said means for supplying oxygen-containing gas comprises a plurality of exit openings arranged symmetrically about the longitudinal axis of said fuel supply nozzle to increase the suction effect of the oxygen-containing gas on the combustion gases drawn into said prechamber means.

United States Patent 11 1 Von Linde et al.

[ Mar. 4, 1975 1 BURNER UNIT [73] Assignee: said Robert von Linde, bysaid Joachim von Linde and German Kurz 22 Filed: Jan. 14, 1974 211 Appl.190.; 432,955

[30] Foreign Application Priority Data Jan. 24, 1973 Germany 2303280,

[52] US. Cl. 431/116, 431/9 [51] Int. Cl. F23m 3/14 [58] Field of Search431/115, 116, 9,158

[56] References Cited 1 UNITED STATES PATENTS 2,918,117 12/1959 Griffin431/116 3,741,166 6/1973 Bailey 431/116 X FOREIGN PATENTS ORAPPLICATIONS 158,763 9/1954 Austria 431/116 Primary E.\'aminerEdWard G.Favors Attorney, Agent, or Firm- Kane, Dalsimer, Kane, Sullivan andKurucz 57 ABSTRACT A burner unit for fluid fuels and also for pulverizedcoal comprising combustion chamber means, prechamber means, means toenable combustion gases to pass from said combustion chamber means intosaid prechamber means, mixing pipe means in communication with saidprechamber means and said combustion chambers means, a fuel supplynozzle for distributing finely divided fuel towards said mixing pipemeans into the drawn-in combustion gases, and means for supplyingoxygen-containing gas, f.i. air, to the mixture of fuel and combustiongases, wherein said means for supplying oxygen-containing gas comprisesa plurality of exit openings arranged symmetrically about thelongitudinal axis of said fuel supply nozzle to increase the suctioneffect of the oxygen-containing gas on the combustion gases drawn intosaid prechamber means.

7 Claims, 4 Drawing Figures PAIENIEMR 3.869.244

sum 2 9g 3 BURNER UNIT BACKGROUND OF THE INVENTION This inventionrelates to burner units for fluid fuels such as oil, gas or pulverizedcoal which are injected into hot combustion gases drawn back from thecombustion chamber into a prechamber by the suction effect of thecombustion air or other oxygen-containing gas supplied to the unit atrelatively high velocities. Such burner unit is f.i. disclosed in U.S.Pat. No. 3,174,526. In this known burner the combustion air is suppliedthrough an annular gap co-axial with the longitudinal axis of the fuelsupply nozzle and creates a suction effect in the prechamber wherebycombustion gases are drawn back from the combustion chamber. The mainadvantage of such burners is the fact that the fuel is mixed with thehot combustion gases prior to the admixture of combustion air so thatthe fuel has good ignition properties when it comes in contact with thecombustion air. This improves combustion considerably. However, theknown burner suffers from some difficulties one of which is thenecessity that the combustion air supply pipe must cross the path of therecirculated combustion gases which affords complicated parts subjectedto high thermal stresses. Furthermore, the supply of combustion airthrough one nozzle only limits the working range of the burner becauseif the quantity of air is reduced in order to reduce the rate ofcombustion the velocity of the air streaming through the annular nozzleis correspondingly reduced and therefore also the suction effect on therecirculated combustion gases. In practice, therefore, the capacity ofthe burner can be varied only between full load and one third loadwhereas in many applications a variation down to one tenth load would bedesirable.

These difficulties are avoided in the present invention by supplying theoxygen-containing gas f.i. air through a plurality of exit openingsarranged symmetrically about the longitudinal axis of the fuel supplynozzle. Compared with a single annular air supply gap the same quantityof air passes through the plurality of exit openings with much highvelocity so that a higher re duction of the quantity of air is possiblewithout affecting the recirculation of combustion gases. A very simpleand effective means for reducing the air supply is the cutting off ofsome of the exit openings from the air source. The air passing throughthe remaining exit openings has a velocity high enough to ensure properrecirculation of combustion gases even at one tenth load of the burner.

Accordingly, it is an object of the present invention to provide aburner of the type mentioned above which enables variation of the burnercapacity over a comparatively large range without adversely affectingthe combustion qualities.

The exit openings are connected via pipes or passages with pressurizedair supply means. These pipes or passages can be parallel to thelongitudinal axis of the fuel supply nozzle or they can be inclinedthereto with an angle of between 5 and 10, in special cases up to 15.Preferably the exit openings for the combustion air are locateddownstream of the fuel supply nozzle in order to obtain a big prechamberwithin which the combustion gases can react with the fuel before thecombustion air is added.

The exit openings can be combined to individual groups with the openingsof each group being symmetrically arranged about the fuel nozzle axis,whereby each group can be connected or disconnected to or form the airsource in order to vary the capacity of the burner. Furthermore, theexit openings of one group may have a different size of the exitopenings of another group. If only two exit openings are provided theyare arranged diametrically opposed and may have different sizes, thesmaller opening only being supplied with air at low load.

Normally the exit openings will be arranged outside the prechamber andf.i. in the wall of the mixing pipe. Nozzles can be inserted in the exitopenings.

The connection and disconnection of individual exit openings or groupsof exit openings can take place outside the bumer by means of valves inthe supply pipes.

Further objects, features and advantages of the present invention willbecome apparent from the following description in connection with thedrawings which show, for purposes of illustration only, some embodimentsin accordance with the present invention.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional elevational view of afirst embodiment of a burner unit according to the invention;

FIG. 2 is a cross-sectional view taken along line AA of FIG. 1;

FIG. 3 is a sectional elevational view of a second embodiment of aburner unit according to the invention with the combustion chamberomitted; and

FIG. 4 is a sectional elevational view of a third embodiment of a burnerunit accordingto the invention.

DETAILED DESCRIPTION OF THE EMBODIMENT Referring now to FIGS. 1 and 2,reference numeral 7 designates a combustion chamber having a refractorylining l1 and an outlet opening 12 for the burnt gases. The combustionchamber 7 is flanged to a burner assembly generally designated 20comprising an outer shell 21 and an inner shell 5. Centrally withininner shell 5 is arranged a mixing pipe 6 having a flange 22 withopenings 23. A fuel supply nozzle 1 is arranged in the inner shell 5co-axial with the longitudinal axis 24 of the burner unit. The space 4between outer shell 21 and inner shell 5 is connected by a connector 3to a blower (not shown) which supplies the combustion air. Pipes 2extend from the space 4 into the prechamber 25 enclosed by inner shell 5and extending up to the mixing pipe 6.

In operation the combustion air is supplied through connector 3 to space4 and through pipes 2 into the prechamber 25. By the injector effect ofthe air streaming out of pipes 2 combustion gases are sucked back fromthe:.combustion chamber 7 through the openings.-,

23 in flange 22, through annular chamber 8 into prechamber 25 where theyare mixed with the fuel emerging from fuel nozzle 1. The finely dividedfuel reacts with the hot combustion gases and forms reduction productsof a precombustion. These products are delivered into the mixing pipe 6by the air jets and are mixed with the air. The mixture of fuel,recirculated combustion gases, reduction products and air emerges fromthe exit opening 9 of the mixing pipe 6 and is ignited by the flamevortex l0. Naturally the first ignition is effected by the usualignition device (not shown). The burning of the mixture takes place inthe combustion chamber 7.

react with the combustion gases.

As can be seen from FIG. 2, the recirculated combustion gases can flowthrough the interstices between the pipes 2 into the space surroundingthe fuel nozzle 1. In this embodiment three groups of air pipes areformed namely a, a; b, b and c, c. Each group can be individuallyconnected to or disconnected from the air supply. For full load allgroups are supplied with air whereas for partial load one or two groupsare disconnected. For this purpose a rotary valve 13 showndiagrammatically in FIG. 1 can be provided.

The embodiment of FIG. 3 differs from the embodiment of FIG. 1 only by ashorter mixing pipe 6 and longer air supply pipes 2'. Again therecirculated combustion gases enter partially the space around fuelnozzle 1 through the interstices between the air pipes 2., and partiallythey mix directly with the combustion air. As can be seen, the exitopenings of pipes 2' are a relatively great distance from the fuelnozzle 1, thus enabling a long reaction of the fuel with therecirculated combustion gases prior to the admixture of the combustionair.

In the embodiment of FIG. 4 the combustion air is supplied to theinterior of the mixing pipe 46 through openings 42 and 42' which areconnected to annular chambers 48, 49 respectively, which are in turnconnected to air supply pipes 43, 43. The air jets emerging from theopenings 42 and 42 into the mixing pipe 46 in direction towards thecombustion chamber 7 generate a pressure rise in the downstream portion46' of the mixture pipe. This pressure rise effects a recirculation ofhot combustion gases from the combustion chamber 7 through passages 41in the wall of the mixing pipe 46 into the prechamber 50 accommodatingduel nozzle 1. The fuel which mixes with the hot combustion gases hasrelatively long time to react therewith until it reaches the air exitopenings 42, 42'. In this example the combustion chamber 7, which, owingto the good preparation of the fuel and the intimate mixing with thecombustion air can be run with very high performance, is liquid-cooled.i

The air exit openings 42 of the one group are of smaller cross-sectionthan the air exit openings 42' of the other group. The openings of eachgroup are equally spaced around the circumference of mixing pipe 46 withone opening of one group always between two openings of the other group.According to the desired performance of the burner the one or the otheror both groups are supplied with combustion air. This burner isespecially suited for operation with liquid hydrocarbons which are burntwith blue flame without generation of soot and even in substochiometricmixture. However, also all combustible gases, particularly the gaseoushydrocarbons, can be burnt.

The burner of the present invention is also well suited for burningpulverized coal owing to the long reaction time available prior to themixing with the combustion air. Furthermore, it should be pointed outthat the burner can be operated with oxygen instead of air. Finally itshould be remarked that the combustion air flowing through space 4 isheated and at the same time forms a heat isolation for the prechamberand the space 8 through which the combustion gases are recirculated.

Thus the several aforenoted objects and advantages are most effectivelyattained. Although several somewhat preferred embodiments have beendisclosed and described in detail herein, it should be understood thatthis invention is in no sense limited thereby and its scope is to bedetermined by that of the appended claims.

What we claim is:

1. A burner unit comprising combustion chamber means, prechamber means,means to enable combustion gases to pass from said combustion chambermeans into said prechamber means, mixing pipe means in communicationwith said prechamber means and said combustion chamber means, a fuelsupply nozzle for distributing finely divided fuel towards said mixingpipe means into said recirculated combustion gases, and means forsupplying oxygen-containing gas to the mixture of fuel and combustiongases, wherein said means for supplying oxygen-containing gas comprisesa plurality of exit openings arranged symmetrically about thelongitudinal axis of said fuel supply nozzle, said means for supplyingoxygen-containing gas comprises pipes extending into the prechamber andarranged symmetrically about the fuel supply nozzle, the intersticesbetween adjacent pipes forming passageways for the recirculatedcombustion gases into the space of the prechamber surrounding the fuelsupply nozzle.

2. A burner unit according to claim 1, wherein said pipes aresubstantially parallel to the longitudinal axis of the fuel supplynozzle.

3. A burner unit according to claim 1, wherein said pipes are inclinedtowards the longitudinal axis of the fuel supply nozzle with an angle upto 15, preferably between 5 and 10.

4. A burner unit comprising combustion chamber means, prechamber means,means to enable combustion gases to pass from said combustion chambermeans into said prechamber means, mixing pipe means in communicationwith said prechamber means and said combustion chamber means, a fuelsupply nozzle for distributing finely divided fuel towards said mixingpipe means into said recirculated combustion gases, and means forsupplying oxygen-containing gas to the mixture of fuel and combustiongases, wherein said means for supplying oxygen-containing gas comprisesa plurality of exit openings arranged symmetrically about thelongitudinal axis of said fuel supply nozzle, at least two groups ofexit openings being provided with each group being connected ordisconnected separately to or from a combustion air supply source.

5. A burner unit comprising combustion chamber means, prechamber means,means to enable combustion gases to pass from said combustion chambermeans into said prechamber means, mixing pipe means in communicationwith said prechamber means and said combustion chamber means, a fuelsupply nozzle for distributing finely divided fuel towards said mixingpipe means into said recirculated combustion gases, and means forsupplying oxygen-containing gas to the mixture of fuel and combustiongases, wherein said means for supplying oxygen-containing gas comprisesa plurality of exit openings arranged symmetrically about thelongitudinal axis of said fuel supply nozzle, the exit openings beingarranged in the inner surface of the mixing pipe and being connected toa source of oxygen-containing gas via annular spaces in the wall of themixing pipe.

6. A burner unit according to claim 5, wherein two groups of exitopenings are provided with each group being individually connectable toor disconnectable 5 two adjacent exit openings of from a source ofoxygen-containing gas.

7. A burner unit according to claim 6, wherein the exit openings of theone group have a bigger crosssection than the exit openings of the othergroup with one exit opening of one group being located between

1. A burner unit comprising combustion chamber means, prechamber means,means to enable combustion gases to pass from said combustion chambermeans into said prechamber means, mixing pipe means in communicationwith said prechamber means and said combustion chamber means, a fuelsupply nozzle for distributing finely divided fuel towards said mixingpipe means into said recirculated combustion gases, and means forsupplying oxygencontaining gas to the mixture of fuel and combustiongases, wherein said means for supplying oxygen-containing gas comprisesa plurality of exit openings arranged symmetrically about thelongitudinal axis of said fuel supply nozzle, said means for supplyingoxygen-containing gas comprises pipes extending into the prechamber andarranged symmetrically about the fuel supply nozzle, the intersticesbetween adjacent pipes forming passageways for the recirculatedcombustion gases into the space of the prechamber surrounding the fuelsupply nozzle.
 2. A burner unit according to claim 1, wherein said pipesare substantially parallel to the longitudinal axis of the fuel supplynozzle.
 3. A burner unit according to claim 1, wherein said pipes areinclined towards the longitudinal axis of the fuel supply nozzle with anangle up to 15*, preferably between 5* and 10*.
 4. A burner unitcomprising combustion chamber means, prechamber means, means to enablecombustion gases to pass from said combustion chamber means into saidprechamber means, mixing pipe means in communication with saidprechamber means and said combustion chamber means, a fuel supply nozzlefor distributing finely divided fuel towards said mixing pipe means intosaid recirculated combustion gases, and means for supplyingoxygen-containing gas to the mixture of fuel and combustion gases,wherein said means for supplying oxygen-containing gas comprises aplurality of exit openings arranged symmetrically about the longitudinalaxis of said fuel supply nozzle, at least two groups of exit openingsbeing provided with each group being connected or disconnectedseparately to or from a combustion air supply source.
 5. A burner unitcomprising combustion chamber means, prechamber means, means to enablecombustion gases to pass from said combustion chamber means into saidprechamber means, mixing pipe means in communication with saidprechamber means and said combustion chamber means, a fuel supply nozzlefor distributing finely divided fuel towards said mixing pipe means intosaid recirculated combustion gases, and means for supplyingoxygen-containing gas to the mixture of fuel and combustion gases,wherein said means for supplying oxygen-containing gas comprises aplurality of exit openings arranged symmetrically about the longitudinalaxis of said fuel supply nozzle, the exit openings being arranged in theinner surface of the mixing pipe and being connected to a source ofoxygen-containing gas via annular spaces in the wall of the mixing pipe.6. A burner unit according to claim 5, wherein two groups of exitopenings are provided with each group being individually connectable toor disconnectable from a source of oxygen-containing gas.
 7. A burnerunit according to claim 6, wherein the exit openings of the one grouphave a bigger cross-section than the exit openings of the other groupwith one exit opening of one group being located between two adjacentexit openings of the other group.